1. Field of the Invention
The present invention relates generally to a bellows process in production of the bellows. More particularly, the invention relates to a bellows for expandably and/or contractibly insulating movable portions of machineries so as to protect from external disturbance factor, such as dust, light beam, humidity and so forth.
2. Description of the Background Art
In the prior art, as shown in FIG. 2, a sheet material 1 which is formed by coating a neoprene rubber on a woven fabric, is pressed into a plurality of essentially channel-shaped pieces 2, 2a, 2b, 2c, . . . having an outer edge 5 and an inner edge 4 by completely cutting along cut edges 4a and 5c, as shown in FIG. 2(b). Then, each two pieces 2, 2a and 2b, 2c, . . . are piled together. The mating inner edges 4 of the piled pieces are sewn along a sewing lines 4c to form an individual bellows segment, as shown in FIG. 2(c). The sewing along the sewing line 4c which extend along the inner edge 4 will be hereafter referred to as "inside sewing". After completing the inside sewing process for forming necessary number of bellows segments, adjacent pieces, such as pieces 2a and 2b in FIG. 2(d) of the adjacent bellows segments are sewn along sewing lines 5b which extend along the outer edge 5 for connecting adjacent bellows segments. The sewing along the sewing line 5b will be hereafter referred to as "outside sewing". Therefore, in the final product of the bellows, the inside sewing and the outside sewing are provided in alternating fashion.
It is possible to provide tack bonding along respective sewing lines 4c and 5b upon piling pieces in advance of performing sewing process in order to facilitate sewing process and to prevent the piled pieces from causing displacement during sewing process.
In such conventional process, since the pieces are completely separated, piling of respective individual pieces with precisely aligning peripheral edges either for the inside sewing process or for the outside sewing process, is time consuming and labor intensive work. Furthermore, since displacement in the piled pieces during sewing process may results in distortion of the final products, relatively high skill of the experienced labor is required for performing sewing process to make the sewing process as cost intensive process as well. Although tack bonding along the sewing lines may prevent the problem of causing displacement during sewing process, process of tack bonding is also time consuming and labor intensive work.